Identification of a novel T-cell epitope in soluble egg antigen of Schistosoma japonicum.

Identification of T-cell epitopes harbored in soluble egg antigen (SEA) of Schistosoma japonicum and study of the immunological properties are essential for understanding the immunopathology and the control of schistosomiasis. As a follow-up to our previous work, the 66- to 80-kDa fragment from SEA was partially digested with protease, fractionated by reverse-phase high-pressure liquid chromatography, and found to be carrying a peptide which stimulated proliferation and gamma interferon (IFN-gamma) production of Th1 clones specific to SEA. Sequence analysis showed that the peptide was composed of 12 amino acids lined up as DLAVELAYLGNL. A synthetic homologue induced proliferation and IFN-gamma and interleukin-2 (IL-2) production, but not IL-4 or IL-6 production, by the Th1 clones as well as by the spleen cells from SEA-immunized mice, thus indicating that the peptide carries a Th1 epitope of SEA.